1. Field of the Invention
The present invention relates to a stereoscopic display apparatus which allows an observer to observe a stereoscopic image by using the parallax between the right and left eyes, an information processing apparatus, a host computer for controlling the display apparatus, and a method therefor, thereby providing an operation environment for comfortable stereoscopic display.
2. Related Background Art
In general, a stereoscopic image display apparatus of the parallax barrier scheme is known well as an apparatus for displaying a stereoscopic image. The parallax barrier scheme is disclosed in S. H. Kaplan, “Theory of Parallax Barriers.”, J. SMPTE, Vol. 59, No. 7, pp. 11-21 (1952). According to this scheme, a striped image obtained by alternately arranging at least right and left images of a plurality of parallax images from a plurality of viewpoints into a vertically striped pattern is observed through a slit pattern (called a parallax barrier) having predetermined opening portions placed at a predetermined distance from this image. With this operation, the observer observes images corresponding to the respective eyes with the corresponding eyes. Japanese Patent Laid-Open Nos. 3-119889 and 5-122733 disclose stereoscopic display apparatuses in which a parallax barrier is electronically generated by a transmission type liquid crystal display device and the like, and the shape and position of each stripe are variably controlled to improve the compatibility with conventional 2D image display apparatuses.
FIG. 19 shows the basic arrangement of the stereoscopic image display apparatus disclosed in Japanese Patent Laid-Open No. 3-119889. This stereoscopic image display apparatus includes a transmission type liquid crystal display apparatus 101 for displaying images and an electronic parallax barrier 103 constituted by a transmission type liquid crystal display placed on the liquid crystal display apparatus 101 sandwiching a spacer 102 having a thickness d.
The transmission type liquid crystal display apparatus 101 displays a vertically striped image consisting of parallax images sensed from two or more directions. A parallax barrier pattern is formed at an arbitrary position on the barrier surface of the electronic parallax barrier 103 upon designation of X and Y addresses by a control means such as a microcomputer, thereby allowing a stereoscopic vision based on the principle of the above parallax barrier scheme. Note that when this electronic parallax barrier is made colorless and transparent throughout the entire image display area, a 2D image can be displayed, thus realizing the compatibility between the 2D display and 3D display.
An apparatus capable of performing mixed display of 3D and 2D images within a single frame is disclosed in Japanese Patent Laid-Open No. 5-122733. In this apparatus, as shown in FIGS. 20A and 20B, a striped barrier pattern can be generated only in a partial area of the electronic parallax barrier 103.
The lenticular scheme is also known widely as a means for displaying a stereoscopic image by using the parallax between the right and left eyes of an observer as in the parallax barrier scheme. In the lenticular scheme, a lenticular lens constituted by an array of many semicylindrical lenses is placed on the front surface of a display to spatially separate an image into images for the right and left eyes, thereby allowing the observer to observe a stereoscopic image. In the display of the lenticular scheme as well, an image displayed on the screen is a vertically striped image obtained by alternately arranging right and left images.
As a stereoscopic display using a horizontally striped image obtained by alternately arranging right and left images, Cyberbook (trademark) is available from Vrex Inc. In this display, as shown in FIG. 21, a striped polarizing plate 202 obtained by alternately arranging two types of polarizing plates, whose polarization axis directions are perpendicular to each other, in units of horizontal lines is placed on the front surface of the liquid crystal display of a notebook personal computer 201. A displayed image is observed through polarization glasses 203 having the two types of polarizing plates corresponding to those used for the striped polarizing plate 202 arranged for the right and left eyes. (In FIG. 21, the arrows indicate polarizing direction of the polarizing direction of the polarizing plates.) With this arrangement, of the displayed image, lines to be seen with the right and left eyes of the observer can be separated/selected. For example, the odd lines of the liquid crystal display are used as right-eye image display lines, and the even lines are used as left-eye image display lines to allow the observer to separately observe images formed by the respective lines with the corresponding eyes.
Various environments in which 3D displays are used can be conceived. Assume that an entire screen is occupied by a single type of image as in the case of a television set. In this case, the relative positional relationship between a displayed image and each constituent element of the apparatus always remains the same. Once, therefore, the observer sets his/her eyes at an optimal observation position, he/she can continuously obtain a proper stereoscopic vision. Assume that a plurality of windows are opened on one screen, and images are to be displayed in the respective windows like images handled in a computer. In this case, as the positions of the windows change, the relationship between each image and each constituent element of the apparatus changes. As a result, the optimal observation position changes, and hence the observer cannot always obtain a proper stereoscopic vision.
When, for example, a barrier 1 of the parallax barrier scheme and a striped image 2 displayed on the image display apparatus maintain a proper relative positional relationship, as shown in FIG. 22, light forming an image for the left eye propagates to a left eye 3, and light forming an image for the right eye propagates to a right eye 4. As a result, the observer can properly recognize a stereoscopic image.
If, however, the relative positions of the barrier 1 and the striped image 2 displayed on the image display apparatus are shifted by one pitch in the horizontal direction with respect to the positions in FIG. 22, as shown in FIG. 23, light forming an image for the left eye propagates to the right eye 4, and light forming an image for the right eye propagates to the left eye 3. As a result, a “reversed stereoscopic vision” for the observer is produced.
When a plurality of windows are opened, and stereoscopic images are displayed in the respective windows, in particular, stereoscopic visions may be properly produced in some windows, but reversed stereoscopic visions may be produced in other windows.
When windows are opened, and images are displayed in the respective windows in this manner, since the relative positions of the barrier 1 and the striped image 2 are likely to change, the possibility of the occurrence of a reversed stereoscopic vision is high. This tendency applies to any stereoscopic display scheme, as well as the parallax barrier scheme, in which the relative positional relationship between a displayed image and other optical parts is important.
The same applies to Cyberbook available from Vrex, which uses a “horizontally striped” parallax image as a striped image. In this case, when, for example, the relative positions of a striped polarizing plate and a striped image displayed on the image display apparatus are shifted by one pitch in the vertical direction, a reversed stereoscopic vision is produced.